Abstract:Objective To investigate the expression level and clinical significance of Apolipoprotein C1 (APOC1) in papillary thyroid carcinoma (PTC) and paracarcinoma(PC) tissues. Methods UALCAN database and the HPA database were adopted to compare the differential expression of APOC1 mRNA in PTC and PC tissues, Kaplan-Meier Plotter database to predict the value APOC1 for PTC prognosis, and TIMER database to study the association of APOC1 with immune cells. The drug targets and cancer-related pathways of the top 5 key genes in PTC were analyzed using the GSCALite database. Finally, GSEA analysis was performed on the APOC1 gene. Results APOC1 mRNA expression level in PTC tissue was significantly higher than that in PC tissue, and the expression levels in PTC tissues of different clinical stages, patients’ age and gender, and lymph node metastasis were significantly higher than those in PC tissue respectively. APOC1 was associated with prognosis and immune infiltration of PTC.APOC1 was associated with multiple cancer pathways and could be suppressed by abiraterone, GSK-J4, and SR8278. And GSEA single-gene functional enrichment analysis revealed that APOC1 functions enriched in propionic acid metabolism, valine and isoleucine, tricarboxylic acid cycle, taurine metabolism, JAK-STAT signaling pathway, autoimmune thyroid disease, apoptosis, cancer signaling pathway, NOTCH signaling pathway, MAPK signaling pathway (P<0.05). Conclusion The APOC1 gene is highly expressed in PTC and associated with prognosis and immune infiltration of PTC, which indicates that APOC1 may be a potential target for PTC diagnosis, prognosis, and drug therapy.